The present invention generally relates to a system for use in determining the location of hidden water pipes and, more particularly, to a system having a transmitter for generating a signal in a target pipe, and to a detector for inductively picking up the signal, amplifying the signal and filtering unwanted electronic noise.
Water, gas and fuel lines are commonly buried beneath the ground. In addition, water, gas and fuel pipes travel beneath or within the foundations and within the walls of buildings. When a leak or partial break in a line occurs, it is necessary to know the location of the line as a first step in determining the location of the leak. A further problem arises because there may be multiple pipes located near each other, and a need exists for a way to determine the location of the particular pipe that requires repair. An additional reason for a line tracing system is that when drilling through the earth, a building wall or foundation, it is desirable to know the location of lines to avoid causing accidental breaks.
A line tracing system operates on the principle of inducing an electromagnetic field in a segment of line (the target line), and then detecting this magnetic field using wound coil of wire. A line tracing system is composed of two major components: a transmitter and a detector. The transmitter is the part of the system used to energize a segment of a water line. The detector senses the energized line and creates an audible tone indicating that the energized line has been detected. An operator passes the detector back and forth over the area to be searched, first to locate the signal and then to determine the location of the strongest signal. The transmitter may send the signal in pulses to aid in distinguishing the transmitter signal from other signals. When operated together, the transmitter and detector form a system that can be effectively used for locating water lines hidden behind walls, within concrete foundations or underground.
A target line may be located near electrical lines which emit electromagnetic signals in the 60 Hz range. In addition, a target line may have branch lines such as water lines to a kitchen, one or more bathrooms and a garage. Target lines passing through concrete foundations may contact or be located near steel rebar. Therefore, a need exists for a line tracer system that can distinguish the target line from branch lines, electrical lines and metal objects. A need exists for a line tracing transmitter with a tone rate that is significantly faster than electrical power signals. A further need exists for a line tracer transmitter than can pulse sufficiently fast so that an operator will not pass over a target line between pulses. In addition, a need exists for a line tracer detector that can filter unwanted electrical noise, provide a visual indication of signal strength, and be physically designed to help the operator search efficiently.
The invention that meets the needs identified above is a line tracer comprising a transmitter for generating a signal in a target pipe, a cable set, a detector for amplifying the signal and filtering unwanted electronic noise, and a method for employing the line tracer. The transmitter further comprises a transmitter circuit board having a pulse generation circuit, a tone generation circuit and a transformer drive circuit. The transmitter circuit board is tuned to provide a pulse frequency of approximately 1.3 Hz and a tone rate of approximately 600 Hz. The detector further comprises a detector circuit board having a difference amplifier, a first high pass filter, a second high pass filter, a non-inverting amplifier, and a sensitivity meter. The detector circuit board is designed to amplify the detected signal and to achieve an attenuation of frequencies from 0 Hz to 400 Hz that is 80 dB/decade. The detector provides a visual indicator of signal strength.